MOCK - Tell us what strange gear you've installed ROCK on!

(Chris) #144

I’m putting a ROCK in a KVM VM for testing purposes (the testing is in another thread). Hence the info in this thread is quite interesting.

On a note related to Wizardofoz’s post showing his A/B testing setup, this is how I A/B DACs:

The Mackie BigKnob Passive has two sets of balanced source and two sets of balanced monitor (TRS) jacks, plus headphone.

  • Passive
  • Volume (down to -100dB)
  • Stereo / Mono
  • Mute
  • Dimm
  • No clicks whatsoever (!) switching source and/or monitor

So, if someone pushes the source select, and you listen and have your eyes closed, you hear nothing except the difference between the two sources. And if you group those in Roon and then match their volumes, you have a fully blind A/B test.

Seen in the picture are an RPI 3 B+ with a HifiBerry DAC+ Pro XLR (balanced) and an ifi iDAC 2 (unbalanced), which I am comparing trying to decide which I like best. :brain:


(Chris) #145

What does the switcher do to the sound, perhaps you ask?
Not much:

Frequency Response
0 dBu Input: ±1 dB, 10 Hz – 30 kHz
Distortion (THD+N)
0 dBu Input @1 kHz: <0.005 %
Crosstalk (20 Hz – 20 kHz)
0 dBu Input @1 kHz: <–85 dB
Muted: –100 dB
Signal-To-Noise Ratio
A–weighted: <–100 dB

For A/B purposes, I guess you could say it doesn’t even have to have such great specs, as long as the sources are both affected the same you can make a comparison. Of course it helps that the switcher is as transparent as possible, so you can hear the most of your sources.

When I am not comparing DACs, I connect my amps directly to whatever unit I’m using, so the BigKnob is not in the chain all the time.

However, as stated, I find it not audible (however, and there is the joke; I’d have to A/B with and without the switcher to state that objectively, right?) :wink:


(Chris) #146


here then a post detailing a ROCK running in a Linux KVM VM on a CentOS 7.6 Server.

The VM has 2GB and 2 vCPUs, a SATA disk (using a 20GB qcow3 disk image), because sadly VirtIO disk drivers are not included in the ROCK image, but nicely enough a VirtIO network card worked fine.

ROCK says Roon Database has 91% of 16 GB available with about 11,000 Songs indexed.

Performance is fine, and seems to be the same as on a Roon core running in a Windows 10 VM, and same as a Roon core running natively on the CentOS Server.

Two disadvantages of ROCK seem to be a) doesn’t run extensions b) is fixed to a UTC time zone, causing Squeezeboxen to show UTC time.


Is there a known-safe motherboard for a ROCK machine, if a NUC isn't quite working out?